Lithium phosphate derivative compounds as Li super-ionic conductor, solid electrolyte and coating layer for lithium metal battery and lithium-ion battery

ABSTRACT

Solid-state lithium ion electrolytes of lithium phosphate derivative compounds are provided which contain an anionic framework capable of conducting lithium ions. The activation energy of the lithium phosphate derivative compounds is from 0.2 to 0.45 eV and conductivities are from 0.01 to 10 mS/cm at 300K. Materials of specific formulae are provided and methods to alter the composite materials with inclusion of aliovalent ions shown. Lithium batteries containing the composite lithium ion electrolytes are also provided. Electrodes containing the lithium phosphate derivative materials and batteries with such electrodes are also provided.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

The disclosure herein is a result of joint research effort conductedunder a joint research agreement between TOYOTA MOTOR ENGINEERING &MANUFACTURING NORTH AMERICA, INC. having an address of 6565 HeadquartersDrive W1-3C, Plano, Tex., 75024, and UNIVERSITY OF MARYLAND, COLLEGEPARK having an address of 2130 Mitchell Bldg. 7999 Regents Dr. CollegePark, Md., 20742.

FIELD OF THE DISCLOSURE

This disclosure is directed to novel lithium phosphate derivativecompounds useful as a Li super-ionic conductor, solid electrolytescontaining the novel lithium phosphate derivative compounds, and anelectrode coating layer for a Li metal battery and a Li-ion batterycontaining the novel lithium phosphate derivative compounds.

BACKGROUND

Li-ion batteries have traditionally dominated the market of portableelectronic devices. However, conventional Li-ion batteries containflammable organic solvents as components of the electrolyte and thisflammability is the basis of a safety risk which is of concern and couldlimit or prevent the use of Li-ion batteries for application in largescale energy storage.

Replacing the flammable organic liquid electrolyte with a solidLi-conductive phase would alleviate this safety issue, and may provideadditional advantages such as improved mechanical and thermal stability.A primary function of the solid Li-conductive phase, usually calledsolid Li-ion conductor or solid state electrolyte, is to conduct Li⁺ions from the anode side to the cathode side during discharge and fromthe cathode side to the anode side during charge while blocking thedirect transport of electrons between electrodes within the battery.

Moreover, lithium batteries constructed with nonaqueous electrolytes areknown to form dendritic lithium metal structures projecting from theanode to the cathode over repeated discharge and charge cycles. If andwhen such a dendrite structure projects to the cathode and shorts thebattery energy is rapidly released and may initiate ignition of theorganic solvent.

Therefore, there is much interest and effort focused on the discovery ofnew solid Li-ion conducting materials which would lead to an all solidstate lithium battery. Studies in the past decades have focused mainlyon ionically conducting oxides such as for example, LISICON(Li₁₄ZnGe₄O₁₆), NASICON (Li_(1.3)Al_(0.3)Ti_(1.7)(PO₄)₃), perovskite(for example, La_(0.5)Li_(0.5)TiO₃), garnet (Li₇La₃Zr₂O₁₂), LiPON (forexample, Li_(2.88)PO_(3.73)N_(0.14)) and sulfides, such as, for example,Li₃PS₄, Li₇P₃S₁₁ and LGPS (Li₁₀GeP₂S₁₂).

While recent developments have marked the conductivity of solid Li-ionconductor to the level of 1-10 mS/cm, which is comparable to that inliquid phase electrolyte, finding new Li-ion solid state conductors isof great interest.

An effective lithium ion solid-state conductor will have a high Li⁺conductivity at room temperature. Generally, the Li⁺ conductivity shouldbe no less than 10⁻⁶ S/cm. Further, the activation energy of Li⁺migration in the conductor must be low for use over a range of operationtemperatures that might be encountered in the environment. Additionally,the material should have good stability against chemical,electrochemical and thermal degradation. Unlike many conventionallyemployed non-aqueous solvents, the solid-state conductor material shouldbe stable to electrochemical degradation reactivity with the anode andcathode chemical composition. The material should have low grainboundary resistance for usage in an all solid-state battery. Ideally,the synthesis of the material should be easy and the cost should not behigh. Unfortunately, none of the currently known lithium ion solidelectrolytes meet all these criteria. For example, Li₁₀GeP₂S₁₂ fails tomeet the requirement of electrochemical stability and has a high costdue to the presence of Ge, despite its state-of-art Li conductivity.Environmentally stable composite materials having high Li⁺ conductivityand low activation energy would be sought in order to facilitatemanufacturing methods and structure of the battery.

The standard redox potential of Li/Li+ is −3.04 V, making lithium metalone of the strongest reducing agent available. Consequently, Li metalcan reduce most known cationic species to a lower oxidation state.Because of this strong reducing capability when the lithium metal of ananode contacts a solid-state Li⁺ conductor containing cation componentsdifferent from lithium ion, the lithium reduces the cation specie to alower oxidation state and deteriorates the solid-state conductor.

For example, the conductor of formula:Li₃PS₄contains P⁵⁺ in the formula and is thus a secondary cation to the Li⁺.When in contact with Li metal, reduction according to the followingequation occurs (J. Mater. Chem. A, 2016, 4, 3253-3266).Li₃PS₄+5Li→P+4Li₂SP+3Li→Li₃P

Similarly, Li₁₀GeP₂S₁₂ has also been reported to undergo degradationwhen in contact with lithium metal according to the following equations(J. Mater. Chem. A, 2016, 4, 3253-3266):Li₁₀GeP₂S₁₂+10Li→2P+8Li₂S+Li₄GeS₄P+3Li→Li₃P4Li₄GeS₄+31Li→16Li₂S+Li₁₅Ge₄Li₁₀GeP₂S₁₂ contains Ge⁴⁺ and P⁵⁺ and each is reduced as indicated.

In another example, Li₇La₃Zr₂O₁₂, which contains secondary cations La³⁺and Zr⁴⁺ undergoes chemical degradation when in contact with lithiummetal according to the following chemistry (J. Mater. Chem. A, 2016, 4,3253-3266):6Li₇La₃Zr₂O₁₂+40Li→4Zr₃O+41Li₂O+9La₂O₃Zr₃O+2Li→Li₂O+3ZrLa₂O₃+6Li→2La+3Li₂O

Thus, many current conventionally known solid Li-ion conductors suffer astability issue when in contact with a Li metal anode.

The inventors of this application have been studying lithium compoundswhich may serve for future use of solid-state Li+ conductors andprevious results of this study are disclosed in U.S. application Ser.No. 15/626,696, filed Jun. 19, 2017, U.S. application Ser. No.15/805,672, filed Nov. 7, 2017, U.S. application Ser. No. 16/013,495,filed Jun. 20, 2018, U.S. application Ser. No. 16/114,946 filed Aug. 28,2018, U.S. application Ser. No. 16/142,217 filed Sep. 26, 2018, U.S.application Ser. No. 16/144,157 filed Sep. 27, 2018, U.S. applicationSer. No. 16/153,335 filed Oct. 10, 2018 and U.S. application Ser. No.16/155,349 filed Oct. 9, 2018. However, research effort continues todiscover additional materials having maximum efficiency, high stability,low cost and ease of handling and manufacture.

Accordingly, an object of this application is to identify a range offurther materials having high Li ion conductivity while being poorelectron conductors which are suitable as a solid state electrolyte fora lithium ion battery and/or suitable as a protective coating layer foror component of an electrode active material.

A further object of this application is to provide a solid state lithiumion battery and/or Lithium metal battery containing a solid state Li ionelectrolyte membrane and/or electrode containing the material.

SUMMARY OF THE EMBODIMENTS

These and other objects are provided by the embodiments of the presentapplication, the first embodiment of which includes a solid-statelithium ion electrolyte, comprising: at least one material selected fromthe group of materials consisting of compounds of formulae (I), (II),(III), (IV) and (V):Li_(y)(M1)_(3−x1)In₂(PO₄)₃  (I)

wherein x1 is a number from greater than 0 to less than 3, y is a valuesuch that charge neutrality of the formula is obtained, and M1 is atleast one element different from Li selected from elements of groups 1,2, 13 and a transition metal;Li_(y)In_(2−x2)(M₂)_(x2)(PO₄)₃  (II)

wherein x2 is a number from greater than 0 to less than 2, y is a valuesuch that the formula (II) is charge neutral, and M2 is at least oneelement different from In selected from elements of groups 3, 4, 5, 6,8, 9, 11, 13, 14, 16 and 17;Li_(y)In₂P_(3−x3)(M3)_(x3)O₁₂  (III)wherein x3 is from greater than 0 to less than 3, y is a value such thatthe formula (III) is charge neutral, and M3 is at least one elementdifferent from P selected from elements of groups 2, 3, 4, 5, 6, 7, 8,9, 10, 14, 15 and 16;Li_(y)In₂P₃O_(12−x4)(X)₄  (IV)

wherein x4 is from greater than 0 to less than 12, y is a value suchthat the formula (IV) is charge neutral and X is an element differentfrom O selected from elements of groups 16 and 17; andLi₃In₂(PO₄)₃  (V).

In an aspect of the first embodiment a lithium ion (Li⁺) conductivity ofthe solid state lithium ion electrolyte of formulae (I)-(V) is from 10⁻²to 10 mS/cm at 300K.

In another aspect of the first embodiment an activation energy of thecompounds of formulae (I)-(V) is from 0.21 to 0.31 eV.

In a second embodiment, the present disclosure includes a solid-statelithium ion electrolyte, comprising: at least one material selected fromthe group of materials consisting of compounds of formulae (VI), (VII),(VIII), (IX) and (X):Li_(y)(M4)_(z1)B(PO₄)₂  (VI)

wherein z1 is a number from greater than 0 to less than 2, y is a valuesuch that charge neutrality of the formula is obtained, and M4 is atleast one element different from Li selected from elements of groups 1,2, 13 and a transition metal;Li_(y)B_(1−z2)(M5)_(z2)(PO₄)₂  (VII)

wherein z2 is a number from greater than 0 to less than 1, y is a valuesuch that charge neutrality of the formula is obtained, and M5 is atleast one element different from B selected from elements of groups 3,6, 7, 12, 13, 14, 15, 16 and 17;Li_(y)BP_(2−z3)(M6)_(z3)O₈  (VIII)

wherein z3 is a number from greater than 0 to less than 2, y is a valuesuch that charge neutrality of the formula is obtained, and M6 is atleast one element different from P selected from elements of groups 2,3, 4, 5, 6, 7, 8, 9, 10, 14, 15 and 16;Li_(y)BP₂O_(8−z4)(X)_(z4)  (IX)

wherein z4 is from greater than 0 to less than 8, y is a value such thatthe formula (IX) is charge neutral and X is an element different from Oselected from elements of groups 16 and 17; andLi₃B(PO₄)₂  (X).

In an aspect of the second embodiment a lithium ion (L⁺) conductivity ofthe solid state lithium ion electrolyte of formulae (VI)-(X) is from10⁻³ to 12 mS/cm at 300K.

In another aspect of the second embodiment an activation energy of thecompounds of formulae (VI)-(X) is from 0.18 to 0.34 eV.

In a third embodiment a solid state lithium battery is included. Thesolid state lithium battery comprises: an anode; a cathode; and a solidstate lithium ion electrolyte located between the anode and the cathode;wherein the solid state lithium ion electrolyte comprises at least onematerial according to the first, second and third embodiments andaspects thereof.

In special aspects of the third embodiment, the solid state lithiumbattery may be a lithium metal battery or a lithium ion battery.

In a fourth embodiment, an electrode having a current collector, anelectrode active material and a coating layer of a material according toany of formulae (I)-(X) as described in the previous embodiments andaspects thereof is provided.

In a fifth embodiment, an electrode having a current collector, anactive layer comprising an electrode active material and a materialaccording to any of formulae (I)-(X) as described in the previousembodiments and aspects thereof is provided.

In a sixth embodiment, a lithium battery containing any of the the solidstate electrolytes and/or electrodes of the previous embodiments isincluded.

The foregoing description is intended to provide a general introductionand summary of the present disclosure and is not intended to be limitingin its disclosure unless otherwise explicitly stated. The presentlypreferred embodiments, together with further advantages, will be bestunderstood by reference to the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the crystal structure of Li₃In₂(PO₄)₃.

FIG. 2 shows a calculated XRD analysis for Li₃In₂(PO₄)₃ obtained basedon Cu-Kα radiation with wavelength of 1.54184 Å.

FIG. 3 shows a Table listing the major peaks and relative intensitiesfor the XRD analysis of FIG. 2.

FIG. 4 shows the crystal structure of Li₂NaB(PO₄)₂.

FIG. 5 shows a calculated XRD analysis for Li₂NaB(PO₄)₂ obtained basedon Cu-Kα radiation with wavelength of 1.54184 Å.

FIG. 6 shows a Table listing the major peaks and relative intensitiesfor the XRD analysis of FIG. 5.

FIG. 7 shows shows an Arrhenius plot of Li⁺ diffusivity (D) inLi_(3.5)In₂P_(2.5)Ge_(0.5)O₁₂.

FIG. 8 shows shows an Arrhenius plot of Li⁺ diffusivity (D) inNaLi_(2.25)B(P_(0.875)Ge_(0.125)O₄)₂.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout this description, the terms “electrochemical cell” and“battery” may be employed interchangeably unless the context of thedescription clearly distinguishes an electrochemical cell from abattery. Further the terms “solid-state electrolyte” and “solid-stateion conductor” may be employed interchangeably unless explicitlyspecified differently.

In the chemical formulae provided the term “less than” indicates lessthan the full value of the number stated. Thus, “less than” may mean avalue up to 0.9 of the expressed number. For example, if the numberindicated is 3, a number less than 3 may be 2.7. The term greater than 0may mean a positive amount being present, such amount may be as littleas 0.01.

Structural characteristics of effective Li⁺ conducting crystal latticeshave been described by Ceder et al. (Nature Materials, 14, 2015,1026-1031) in regard to known Li⁺ ion conductors Li₁₀GeP₂S₁₂ andLi₇P₃S₁₁, where the sulfur sublattice of both materials was shown tovery closely match a bcc lattice structure. Further, Li⁺ ion hoppingacross adjacent tetrahedral coordinated Li⁺ lattice sites was indicatedto offer a path of lowest activation energy.

The inventors are conducting ongoing investigations of new lithiumcomposite compounds in order to identify materials having the propertieswhich may serve as solid-state electrolytes in solid state lithiumbatteries. In the course of this ongoing study and effort the inventorshave developed and implemented a methodology to identify compositematerials which have chemical and structural properties which have beendetermined by the inventors as indicators of lithium ion conductancesuitable to be a solid state electrolyte for a lithium-ion battery.

To qualify as solid state electrolyte in practical applications, thematerial must meet several certain criteria. First, it should exhibitdesirable Li-ion conductivity, usually no less than 10⁻⁶ S/cm at roomtemperature. Second, the material should have good stability againstchemical, electrochemical and thermal degradation. Third, the materialshould have low grain boundary resistance for usage in all solid-statebattery. Fourth, the synthesis of the material should be easy and thecost should not be high.

A criterion of this methodology requires that to qualify as solid stateelectrolyte in practical application, the material must exhibitdesirable Li-ion conductivity, usually no less than 10⁻⁶ S/cm at roomtemperature. Thus, ab initio molecular dynamics simulation studies wereapplied to calculate the diffusivity of Li ion in the lattice structuresof selected silicate materials. In order to accelerate the simulation,the calculation was performed at high temperatures and the effect ofexcess Li or Li vacancy was considered. In order to create excess Li orLi vacancy, aliovalent replacement of cation or anions may be evaluated.Thus, Li vacancy was created by, for example, partially substituting Siwith aliovalent cationic species while compensating the chargeneutrality with Li vacancy or excess Li. For example, replacing 50% ofSi in Li₁₀Si₂PbO₁₀ with P results in the formation of Li₉PSiPbO₁₀.

The diffusivity at 300 K was determined according to equation (I)D=D₀ exp(−E_(a)/k_(b)T)  equation (I)where D₀, E_(a) and k_(b) are the pre-exponential factor, activationenergy and Boltzmann constant, respectively. The conductivity is relatedwith the calculated diffusivity according to equation (II):σ=D₃₀₀ ρe ²/k_(b)T  equation (II)where ρ is the volumetric density of Li ion and e is the unit charge.

The anionic lattice of Li-ion conductors has been shown to match certainlattice types (see Nature Materials, 14, 2015, 2016). Therefore, in theanionic lattice of the potential Li⁺ ion conductor is compared to theanionic lattice of Li⁺ ion conductor known to have high conductivity.

Thus, selected lithium phosphate derivative compounds were compared toLi-containing compounds reported in the inorganic crystal structuredatabase (FIZ Karlsruhe ICSD—https://icsd.fiz-karlsruhe.de) andevaluated in comparison according to an anionic lattice matching methoddeveloped by the inventors for this purpose and described in copendingU.S. application Ser. No. 15/597,651, filed May 17, 2017, to match thelattice of these compounds to known Li-ion conductors.

According to the anionic lattice matching method described in copendingU.S. application Ser. No. 15/597,651, an atomic coordinate set for thecompound lattice structure may be converted to a coordinate set for onlythe anion lattice. The anions of the lattice are substituted with theanion of the comparison material and the obtained unit cell resealed.The x-ray diffraction data for modified anion-only lattice may besimulated and an n×2 matrix generated from the simulated diffractiondata. Quantitative structural similarity values can be derived from then×2 matrices.

The purpose of anionic lattice matching is to further identify compoundswith greatest potential to exhibit high Li⁺ conductivity. From thiswork, the compounds described in the embodiments which follow weredetermined to be potentially suitable as solid-state Li⁺ conductors.

Ab initio molecular dynamics (AIMD) simulation was then applied topredict the conductivity of the targeted lithium phosphate derivativecompounds. The initial structures were statically relaxed and were setto an initial temperature of 100 K. The structures were then heated totargeted temperatures (750-1150 K) at a constant rate by velocityscaling over a time period of 2 ps. The total time of AIMD simulationswere in the range of 200 to 400 ps. The Li⁺ diffusivity at differenttemperatures from 750-1150 K follows an Arrhenius-type relationship.

During the course of investigation of specific lithium phosphatederivative materials, the inventors have identified compounds based onLi₃In₂(PO₄)₃ and Li₃BPO₄ as having properties which make them of greatinterest as lithium ion conductors.

Applying equation (I) above the diffusivity at 300 K was determined andthen the conductivity may be determined using the link betweenconductivity and diffusivity of equation (II). Table 1 shows theactivation energy and room temperature conductivity determined forLi_(3.5)In₂P_(2.5)Ge_(0.5)O₁₂ and NaLi_(2.25)B(P_(0.875)Ge_(0.125)O₄)₂.Arrhenius plots of Li⁺ diffusivity are shown for each of these materialsin FIGS. 7 and 8. The determined activation energies and lithium ionconductivities of these materials identifies them as materials suitableas solid state electrolyte and Li ion conductors according to thepresent disclosure.

TABLE 1 Activation energy and room temperature conductivity of targetlithium phosphate derivative compounds from AIMD simulations. σ (mS/cm)at Composition E_(a) (eV) 300K Li_(3.5)In₂P_(2.5)Ge_(0.5)O₁₂ 0.26 1.4NaLi_(2.25)B(P_(0.875)Ge_(0.125)O₄)₂ 0.26 1.0

Accordingly, in one embodiment the present disclosure provides asolid-state lithium ion electrolyte, comprising: at least one materialselected from the group of materials consisting of compounds of formulae(I), (II), (III), (IV) and (V):Li_(y)(M1)³⁻¹In₂(PO₄)₃  (I)

wherein x1 is a number from greater than 0 to less than 3, y is a valuesuch that charge neutrality of the formula is obtained, and M1 is atleast one element different from Li selected from elements of groups 1,2, 13 and a transition metal, preferably a group 1 or 2 element and mostpreferably Na or K;Li_(y)In_(2−x2)(M2)₂(PO₄)₃  (II)

wherein x2 is a number from greater than 0 to less than 2, y is a valuesuch that the formula (II) is charge neutral, and M2 is at least oneelement different from In selected from elements of groups 3, 4, 5, 6,8, 9, 11, 13, 14, 16 and 17, preferably an element from groups 8, 9, 11,13, 14, 16 and 17 and most preferably from groups 8, 9, 11 and 13;Li_(y)In₂P_(3−x3)(M3)_(x3)O₁₂  (III)wherein x3 is from greater than 0 to less than 3, y is a value such thatthe formula (III) is charge neutral, and M3 is at least one elementdifferent from P selected from elements of groups 2, 3, 4, 5, 6, 7, 8,9, 10, 14, 15 and 16, preferably elements of groups 5-10 and mostpreferably groups 8-10;Li_(y) In₂P₃O_(12−x4)(X)_(x4)  (IV)

wherein x4 is from greater than 0 to less than 12, y is a value suchthat the formula (IV) is charge neutral and X is an element differentfrom O selected from elements of groups 16 and 17, preferably group 16.

The compounds of formulae (I) to (IV) are doped materials of thecompound of formula (V):Li₃In₂(PO₄)₃  (V)wherein at least one of Li, In, P and O are aliovalently replaced asdescribed above.

Elements suitable for aliovalent substitution may be selected by anionic substitution probability determined by the method as described byHautier et al. (Inorg. Chem. 2011, 50, 656-663) wherein candidatedopants may be selected by an ionic substitution probabilistic model,constructed upon data mining of all known inorganic crystal materials.Dopants which could potentially create vacancies or interstitials withinthe particular materials were included. The structures with dopants thatwere not energetically favorable would be screened and excluded duringphase stability calculations. The configurations of the sublattices,dopants, and vacancies or interstitials were determined by thecomputation methods described herein. Such methods have been describedfor example, in the following reports:

Bai et al., ACS Appl. Energy Mater. 2018, 1, 1626-1634; and

He et al., Phys. Chem. Chem. Phys., 2015. 17, 18035.

The crystal structure of Li₃In₂(PO₄)₃ is shown in FIG. 1. The compoundof formula (V) and the materials of formulae (I), (II), (III) and (IV)comprise a crystal lattice having a monoclinic structure. A calculatedX-ray diffraction analysis obtained based on Cu-Kα radiation withwavelength of 1.54184 Å for Li₃In₂(PO₄)₃ is shown in FIG. 2 and a Tableshowing the major peak positions (2θ) is shown in FIG. 3.

The inventors have learned that the resulting doped materials accordingto formulae (I) to (IV) retain the crystal structure of the basecompound (V) and have activation energies and conductivity related tothe base compound of formula (V). Based on the measurement methodsdescribed above the lithium ion (Li⁺) conductivity of the compositematerials of formulae (I), (II), (Ill) and (IV) may be from 0.01 to 10mS/cm at 300K, preferably from 0.1 to 10.0 mS/cm at 300K and mostpreferably from 1.0 to 10 mS/cm at 300K. The activation energy of thethe materials of formulae (I), (II), (III) and (IV) may be from 0.21 eVto 0.31 eV, preferably from 0.21 eV to 0.30 eV.

In a second embodiment the present disclosure provides a solid-statelithium ion electrolyte, comprising: at least one material selected fromthe group of materials consisting of compounds of formulae (VI), (VII),(VIII), (IX) and (X):Li_(y)(M4)_(z1)B(PO₄)₂  (VI)

wherein z1 is a number from greater than 0 to less than 2, y is a valuesuch that charge neutrality of the formula is obtained, and M4 is atleast one element different from Li selected from elements of groups 1,2, 13 and a transition metal, preferably a group 1 or 2 element and mostpreferably Na or K;Li_(y)B_(1−z2)(M5)_(z2)(PO₄)₂  (VII)

wherein z2 is a number from greater than 0 to less than 1, y is a valuesuch that charge neutrality of the formula is obtained, and M5 is atleast one element different from B selected from elements of groups 3,6, 7, 12, 13, 14, 15, 16 and 17, preferably an element from groups 6, 7,12, 13, 14, 15 and 16 and most preferably from groups 12-17;Li_(y)BP_(2−z3)(M6)_(z3)O₈  (VIII)

wherein z3 is a number from greater than 0 to less than 2, y is a valuesuch that charge neutrality of the formula is obtained, and M6 is atleast one element different from P selected from elements of groups 2,3, 4, 5, 6, 7, 8, 9, 10, 14, 15 and 16, preferably elements of groups5-10, 14 and 15 and most preferably groups 14-15;Li_(y)BP₂O_(8−z4)(X)₄  (IX)

wherein z4 is from greater than 0 to less than 8, y is a value such thatthe formula (IX) is charge neutral and X is an element different from Oselected from elements of groups 16 and 17 preferably group 16.

The compounds of formulae (VI) to (IX) are doped materials of thecompound of formula (X):Li₃B(PO₄)₂  (X)wherein at least one of Li, B, P and O are aliovalently replaced asdescribed above.

In one special aspect of this embodiment the compound of formula (VI) isa compound of formula (VIa):Li₂NaB(PO₄)₂  (VIa)wherein each of Li, B, P and O may be aliovalently replaced as describedfor each of formulae (VI)-(IX).

The crystal structure of Li₂NaB(PO₄)₂ is shown in FIG. 4. The compoundof formula (VIa) and the materials of formulae (VI), (VII), (VIII), (IX)and (X) comprise a crystal lattice having a triclinic structure. Acalculated X-ray diffraction analysis obtained based on Cu-Kα radiationwith wavelength of 1.54184 Å for Li₂NAB(PO₄)₂ is shown in FIG. 5 and aTable showing the major peak positions (2θ) is shown in FIG. 6.

The resulting doped materials according to formulae (VI) to (X) have thecrystal structure of the compound (VIa) and have activation energies andconductivity related to the compound of formula (VIa). Based on themeasurement methods described above the lithium ion (Li⁺) conductivityof the composite materials of formulae (VI), (VII), (VIII), (IX) and (X)may be from 10⁻³ to 12 mS/cm at 300K, preferably from 0.1 to 12.0 mS/cmat 300K and most preferably from 1.0 to 12 mS/cm at 300K. The activationenergy of the the materials of formulae (VI)-(X) may be from 0.18 eV to0.34 eV, preferably from 0.25 eV to 0.34 eV.

Synthesis of the materials of the embodiments described above may beachieved by solid state reaction between stoichiometric amounts ofselected precursor materials. Exemplary methods of solid state synthesisare described for example in each of the following papers: i)Monatshefte für Chemie, 100, 295-303, 1969; ii) Journal of Solid StateChemistry, 128, 1997, 241; iii) Zeitschrift für Naturforschung B, 50,1995, 1061; iv) Journal of Solid State Chemistry 130, 1997, 90; v)Journal of Alloys and Compounds, 645, 2015, S174; and vi) Z.Naturforsch. 51b, 199652 5. Adaptation of these methods to prepare thecomposite compounds according to the embodiments disclosed herein iswell within the capability of one of ordinary skill in the art.

In further embodiments, the present application includes solid statelithium ion batteries containing the solid-state electrolytes describedabove. Solid-state batteries of these embodiments including metal-metalsolid-state batteries may have higher charge/discharge rate capabilityand higher power density than classical batteries and may have thepotential to provide high power and energy density.

Thus, in further embodiments, solid-state batteries comprising: ananode; a cathode; and a solid state lithium ion electrolyte according tothe embodiments described above, located between the anode and thecathode are provided.

Thus, the present disclosure provides a solid state lithium battery,comprising: an anode; a cathode; and a solid state lithium ionelectrolyte located between the anode and the cathode; wherein the solidstate lithium ion electrolyte comprises at least one material selectedfrom the group of materials consisting compounds of formulae (I), (II),(III), (IV), (V), (VI), (VIa), (VII), (VIII), (IX) and (X) as previouslydescribed including all the elements and aspects previously described.

The anode may be any anode structure conventionally employed in alithium ion battery. Generally such materials are capable of insertionand extraction of Li⁺ ions. Example anode active materials may includegraphite, hard carbon, lithium titanate (LTO), a tin/cobalt alloy andsilicon/carbon composites. In one aspect the anode may comprise acurrent collector and a coating of a lithium ion active material on thecurrent collector. Standard current collector materials include but arenot limited to aluminum, copper, nickel, stainless steel, carbon, carbonpaper and carbon cloth. In an aspect advantageously arranged with thesolid-state lithium ion conductive materials described in the first andsecond embodiments, the anode may be lithium metal or a lithium metalalloy, optionally coated on a current collector. In one aspect, theanode may be a sheet of lithium metal serving both as active materialand current collector.

The cathode structure may be any conventionally employed in lithium ionbatteries, including but not limited to composite lithium metal oxidessuch as, for example, lithium cobalt oxide (LiCoO₂), lithium manganeseoxide (LiMn₂O₄), lithium iron phosphate (LiFePO₄) and lithium nickelmanganese cobalt oxide. Other active cathode materials may also includeelemental sulfur and metal sulfide composites. The cathode may alsoinclude a current collector such as copper, aluminum and stainlesssteel.

In one aspect, the active cathode material may be a transition metal,preferably, silver or copper. A cathode based on such transition metalmay not include a current collector.

In a further set of embodiments, electrodes containing at least onematerial selected from the group of materials consisting compounds offormulae (I), (II), (III), (IV), (V), (VI), (VIa), (VII), (VIII), (IX)and (X) as previously described including all the elements and aspectspreviously described are also disclosed. Thus in the preparation of theelectrode the active material as described above may be physically mixedwith the solid electrolyte material before application to the currentcollector or the solid electrolyte material may be applied as a coatinglayer on the applied active material. In either embodiment the presenceof the lithium ion super conductor on or within the the electrodestructure may enhance performance of the electrode and especially whenapplied as a coating layer, may serve to protect a conventional solidstate electrolyte.

Thus, an embodiment of the present disclosure includes a cathodecomprising a current collector and a layer of cathode active materialapplied to the current collector wherein at least one of the followingcomponents is present: i) the cathode active material applied to thecurrent collector is a physical mixture containing at least one of thesolid electrolyte materials of formulae (I)-(X) including (VIa) asdescribed above; and ii) the layer of cathode active material applied tothe current collector is coated with a layer comprising at least one ofthe solid electrolyte materials of formulae (I)-(X) including (VIa).Cathodes having both elements i) and ii) are also included in thepresent disclosure.

In related embodiments the present disclosure includes an anodecomprising a current collector and a layer of anode active materialapplied to the current collector wherein at least one of the followingcomponents is present: i) the anode active material applied to thecurrent collector is a physical mixture containing at least one of thesolid electrolyte materials of formulae (I)-(X) including (VIa) asdescribed above; and ii) the layer of anode active material applied tothe current collector is coated with a layer comprising at least one ofthe solid electrolyte materials of formulae (I)-(X) including (VIa).

Batteries containing a cathode as described in the above embodiment, ananode described in the above embodiment or containing both an anode andcathode according to the above embodiments are also embodiments of thepresent disclosure.

The above description is presented to enable a person skilled in the artto make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, this invention is not intended to belimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. In thisregard, certain embodiments within the invention may not show everybenefit of the invention, considered broadly.

The invention claimed is:
 1. A solid-state lithium ion electrolyte,comprising: at least one material selected from the group of materialsconsisting of compounds of formulae (I), (II), (III) and (IV):Li_(y)(M1)_(3-x1)In₂(PO₄)₃  (I) wherein x1 is a number from greater than0 to less than 3, y is a value such that charge neutrality of theformula is obtained, and M1 is at least one element different from Liselected from elements of groups 1, 2, 13 and a transition metal;Li_(y)In_(2-x2)(M2)_(x2)(PO₄)₃  (II) wherein x2 is a number from greaterthan 0 to less than 2, y is a value such that the formula (II) is chargeneutral, and M2 is at least one element different from In selected fromelements of groups 3, 4, 5, 6, 8, 9, 11, 13, 14, 16 and 17;Li_(y)In₂P_(3-x3)(M3)_(x3)O₁₂  (III) wherein x3 is from greater than 0to less than 3, y is a value such that the formula (III) is chargeneutral, and M3 is at least one element different from P selected fromelements of groups 2, 3, 4, 5, 9, 10, 14, 15 and 16;Li_(y)In₂P₃O_(12-x4)(X)_(x4)  (IV) wherein x4 is from greater than 0 toless than 12, y is a value such that the formula (IV) is charge neutraland X is an element different from O selected from elements of groups 16and
 17. 2. The solid state lithium ion electrolyte according to claim 1,wherein a lithium ion (Li⁺) conductivity of the solid state lithium ionelectrolyte is from 0.01 to 10 mS/cm at 300K.
 3. The solid state lithiumion electrolyte according to claim 1, wherein an activation energy ofthe material is from 0.21 to 0.31 eV.
 4. The solid state lithium ionelectrolyte according to claim 1, wherein the material comprises amonoclinic structure.
 5. The solid state lithium ion electrolyteaccording to claim 1 wherein an X-ray Diffraction Analysis obtainedbased on Cu-Kα radiation with wavelength of 1.54184 Å, of the materialcomprises the following major peaks: Peak Position Relative Intensity16.044 12.365 19.934 30.619 20.374 100.0 20.676 23.232 22.984 11.73824.066 13.492 28.875 35.491 29.063 13.313 32.541 18.188 32.731 20.85835.154 17.828 35.494 11.833 35.935 11.846 36.038 29.528 41.43 10.5246.465 10.319 56.564 10.449.


6. A solid state lithium battery, comprising: an anode; a cathode; and asolid state lithium ion electrolyte located between the anode and thecathode; wherein the solid state lithium ion electrolyte comprises atleast one material selected from the group of materials consistingcompounds of formulae (I), (II), (III) and (IV):Li_(y)(M1)_(3-x1)In₂(PO₄)₃  (I) wherein x1 is a number from greater than0 to less than 3, y is a value such that charge neutrality of theformula is obtained, and M1 is at least one element different from Liselected from elements of groups 1, 2, 13 and a transition metal;Li_(y)In_(2-x2)(M2)_(x2)(PO₄)₃  (II) wherein x2 is a number from greaterthan 0 to less than 2, y is a value such that the formula (II) is chargeneutral, and M2 is at least one element different from In selected fromelements of groups 3, 4, 5, 6, 8, 9, 11, 13, 14, 16 and 17;Li_(y) In₂P_(3-x3)(M3)_(x3)O₁₂  (III) wherein x3 is from greater than 0to less than 3, y is a value such that the formula (III) is chargeneutral, and M3 is at least one element different from P selected fromelements of groups 2, 3, 4, 5, 6, 7, 9, 10, 14, 15 and 16;Li_(y)In₂P₃O_(12-x4)(X)_(x4)  (IV) wherein x4 is from greater than 0 toless than 12, y is a value such that the formula (IV) is charge neutraland X is an element different from 0 selected from elements of groups 16and
 17. 7. The solid state lithium ion battery according to claim 6,wherein the battery is a lithium metal battery or a lithium ion battery.